The invention relates to air supply systems, and in particular to air supply systems that can be used in clean rooms.
An important semiconductor manufacturing process, such as a lithography (exposure) process, must be performed in a clean room where lithography machines are located. Typically, such a semiconductor manufacturing process is performed under a certain air condition. Namely, airborne molecular contamination (AMC) in the clean room must be precisely controlled, such that the semiconductor manufacturing process can be successfully performed. Airborne molecular contamination can include total organic compound (TOC), NH3, and total sulfur (TS), for example.
Referring to FIG. 1, a conventional clean room 1 includes multiple floors, such as a first floor 11 and a second floor 12. A plurality of machines for manufacturing semiconductors, such as multiple general machines 21 and a critical machine 22, are disposed on one of the floors, such as the second floor 12. As is known, a critical machine may require more highly filtered air than one or more other machines in the clean room. A conventional air supply system is deployed in the clean room 1, providing clean air to the general machines 21 and critical machine 22. The air supply system comprises an intake duct 31, a make-up air unit (MAU) 32, a first air duct 33, an air conditioning cabinet (ACC) 34, a second air duct 35, an exhaust duct 36, and a plurality of fan filter units (FFU) 37. One end of the intake duct 31 is positioned at the exterior of the clean room 1 and the other end is connected to the make-up air unit 32. The make-up air unit 32 and fan filter units 37 are disposed on the second floor 12 of the clean room 1. One end of the first air duct 33 is connected to the make-up air unit 32 and the other end is in the clean room 1. The air conditioning cabinet 34 is disposed on the first floor 11 and is connected to the critical machine 22 by means of the second air duct 35. Specifically, since the critical machine 22 requires extremely clean air, the air conditioning cabinet 34 is provided with a chemical filter (not shown) to further purify the air supplied. Additionally, one end of the exhaust duct 36 is positioned at the exterior of the clean room 1 and the other end is connected to the critical machine 22.
As shown in FIG. 1, air can be drawn into the make-up air unit 32 via the intake duct 31 by a fan (not shown) of the make-up air unit 32. Airborne molecular contamination (contaminants) and particles in the air can be preliminarily removed by the make-up air unit 32. Additionally, the temperature and humidity of the air can be adjusted by the make-up air unit 32. The air flowing through the make-up air unit 32 is transported into the clean room 1 (first floor 11) via first air duct 33. The air then enters the second floor 12 and air conditioning cabinet 34. Accordingly, the air entering the second floor 12 from the first floor 11 can be used by the general machines 21. In another aspect, the air further filtered by the air conditioning cabinet 34 enters the critical machine 22 via the second air duct 35. Waste gas produced in the critical machine 22 can be exhausted via the exhaust duct 36. The fan filter units 37 can produce air circulation in the clean room 1 and filters (not shown) thereof can further remove the particles therein.
Accordingly, during operation of the general machines 21 and critical machine 22, waste gas containing by-products is produced. The waste gas also includes high-concentration airborne molecular contamination. Furthermore, the waste gas typically leaks into the clean room 1 because the air pressure in the general machines 21 and critical machine 22 typically exceeds that of the environment (or in the clean room 1), increasing airborne molecular contamination therein. Under this condition, the lifespan of the chemical filter in the air conditioning cabinet 34 is greatly reduced and the chemical filter must be replaced frequently. The chemical filter, however, is very expensive. Thus, frequent replacement of the chemical filter results in increased manufacturing costs.